Category Archives: Material and Tool Information

Information about mosaic materials and tools.

Mosaic Street-Number Sign by artist Monika Walter damaged

Warning: Marine Plywood Not For Mosaic

Marine plywood cannot be used as a mosaic backer for outdoor and wet mosaic.

Yes, marine plywood can withstand the outdoors and wet days for many years, but it is completely unacceptable as a mosaic backer because it swells and contracts with changes in humidity in the outside air. That amount of swelling and contracting is tiny and might not be significant in construction projects, but it is fatal for mosaic. Absolutely fatal. It’s only a matter of time, and it’s usually not long.

People recommending the use of marine plywood as a backer for outdoor mosaics are not considering one critical detail:

The swelling and contracting of wood due to humidity isn’t trivial where adhesives are concerned, and the displacement (movement) can be measured. Imagine rainy days versus dry days. The displacement is more than enough to work glass free from adhesive because the glass isn’t swelling or contracting at all.

This is not speculation. I am an engineer and have worked in a materials testing lab.

Another piece of evidence I could bring to any argument about the use of marine plywood in mosaic is that I have received photos of tragically-damaged mosaics for 17 years, and marine plywood wins hands down as far as being the worst cause of grief, and the reason is simple:

Marine plywood SEEMS like a solid safe option because contractors will talk about the life they have gotten from it on certain jobs, and so the people who make the mistake of choosing it tend to be people who are making a design with a lot of work and care for the details. They took the time to choose a “good” backer because they knew they were going to put a lot of effort into their mosaic.

Seeing these mosaics damaged is much more painful than seeing some hasty work falling apart because the technical details were just outright neglected.

That brings me to an email I received from Monika Walter.

Artist Monika Walter

Monika Walter says she doesn’t consider herself to be an “artist,” but she has some solid work at her mosaic website, and she makes tables and mirrors and clocks for craft shows. They all look well-executed to me, and a couple of her mosaics make me jealous. More about that later.

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Mosaic Coaster with Scratched Tile by artist Stefi Morrison, detail shot

When To Use Sanded Grout

This article is about why we recommend “the opposite” of what the tile industry recommends for grouting glass mosaics and mosaics with a standard grout gap. This article also explains how to avoid scratching the glass tile while grouting with sanded grout.

Industry Recommendations

The tile industry recommends using sanded grout for gaps 1/8 to 3/8 inch and adding a coarser grade of sand for gaps larger than 3/8 inch. For gaps less than 1/8 inch, which is what mosaic glass mosaics have, tile manufacturers and industry associations recommend using non-sanded grout.

At Mosaic Art Supply, I have always recommended using sanded grout for everything except mosaics with hairline gaps between the tile. Why the difference? There are three reasons.

Plaques not Walls

Many of our customers are making mosaics on small movable surfaces like plaques or tabletops not walls or floors, and these smaller mosaics are subject to being dropped and impacted and vibrated and flexed more than an architectural surface. The sand provides tensile strength and helps the grout not be knocked out of the gaps as easily.

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Crucifix Installed in Niche in Altarpiece by artist Nicholas Vasko

Imitation Gold Glass for Altarpieces and Icons

Religious icons make heavy use of gold leaf glass to represent halos and divine light but also to adorn the figures and to communicate the preciousness of the image. Of course we carry 24 kt Gold Leaf Glass for use in icons and other mosaics, but the material is expensive for obvious reasons, and so the question becomes what do you use when you need to make something larger, such as an altarpiece or a life-size icon?

The answer is the silver-foil glass product known as Imitation Gold Mosaic Glass, which has an epoxy coating over the silver backing to prevent oxidation and blackening by adhesives.

Artist Nicholas Vasco emailed us some pictures of a couple of his recent projects using Imitation Gold Glass, and they are impressive. Both the altarpiece and the mosaic inserts of the chapel entrance way are very well done and worth talking about for several reasons.

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Pelicans mosaic by artists Carl and Sandra Bryant.

Alternatives to Marble Mosaic

Many people are drawn to the idea of making mosaics from marble and stone, mostly because that was the material used by the ancient Romans but also because they would like to make a mosaic from natural materials in subdued colors.

Nevertheless, as soon as these people start trying to source materials, they quickly become frustrated with how limited the color palette is in marble mosaic, and they usually end up mixing the stone with smalti or ceramic or porcelain tiles, or they use dyed stone or synthetic stone for certain colors.

In either case, the mosaic usually doesn’t have the look and feel that was desired, which is really a tragedy because superior results could have been more easily and cheaply accomplished had the artist used all glass and merely restricted the color palette to more subtle hues.

Before you convince yourself you need to work in stone, spend some time looking at glass mosaics made from subdued color pallets.

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Garden Retaining Wall

Mosaic Mural Surface Preparation

The best way to mount an outdoor mosaic mural is to use thinset mortar and mount it directly to a brick, stone, or concrete wall.

You can make mosaic murals on foam-core backer board and mount these backers onto wooden fences with screws, but that is less than ideal for several reasons, and the weight could cause the fence to lean if its posts aren’t securely anchored. That is why we recommend mounting mosaics directly on masonry surfaces (brick, stone, or concrete).

Masonry surfaces need to be cleaned and possibly smoothed before the mosaic is mounted, but that isn’t too difficult, and it is well worth doing if you want the mosaic to last any time at all. Continue reading

Mosaic Street Number

Mosaic Street Number

Natalija decided to test some materials and methods by putting our street number on the loading dock of the warehouse. Her method was to lay 3/4-inch vitreous tile in a mounting grid, but she put them in upside down and laid a sheet of fiberglass mesh on them and used one drop of silicone adhesive on each tile to attach the mesh. My method would be to lay the tiles in the grid right side up and pick up the design with mosaic mounting tape. Continue reading

Second Layer of Mesh

Making Foam-Core Mosaic Backers For Outdoor Projects

Artist Jill Gatwood uses the following method to make water-resistant foam-core mosaic backers for exterior mosaics, such as the Pet Memorial Name Plaques she does for clients who need something that is lighter weight and easier to ship than stone or solid concrete. The method wraps the foam in three or four successive layers of fiberglass mesh and thinset mortar, and that coating is pretty tough, tougher than stone. (The combination of polymer-modified cement and fiberglass can withstand blows that would easily crack granite of the same thickness.) Continue reading

Mosaic Mailbox Jill Gatwood

Mosaics on Steel Mailbox Using Silicone Adhesive

Artist Jill Gatwood has emailed me her procedure for using GE Silicone II to mount mosaic tile to steel mailboxes, and it is outlined below.

Jill’s instructions have convinced me that there are enough mosaic applications for silicone adhesive that we should sell it. Note that we still recommend thinset mortar or Weldbond for mosaics on architectural surfaces such as backsplashes, but for projects such as mosaic  mailboxes or glass-on-glass mosaics, silicone adhesive is preferred.

Jill’s steel mailbox instructions are fairly complete and include recommendations for purchasing the right type of mailbox for the project and modifying it as needed.

Steel Mailbox Instructions

1. Selecting The Mailbox

Jill says that a steel mailbox from the big box home improvement stores or a hardware store will work but you have to check it and make sure the metal is strong and doesn’t flex. (In practical terms, this means you should buy the mid-grade or premium model and not the one made for the bottom of the market.)

Jill recommends getting one that has ribs to strengthen the frame if you need an XL size mailbox. Continue reading

Prying Tile From Finished Mosaic

How To Pry Up Tiles To Modify A Mosaic

I have often used a small screwdriver to pry up tiles when I wanted to change some detail in a mosaic, but in all of those cases, the mosaic had a grout gap, and it was possible to knock an individual tile out or shatter it without damaging its neighbors, at least most of the time.

But what if you can’t afford to damage surrounding tiles or you have a mosaic with no grout gap? Is it even possible to get tiles up? The answer is yes, and the method involves a wet cotton swab, a dental pick, and a sharpened chopstick.

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Mosaic Picture Frame Iso View

Mosaic Picture Frame

Angela made a mosaic picture frame using our irregular glazed ceramic tile and left the sides of the frame uncovered. She also nested the angular shapes to created an abstract pattern without cutting any of the tiles to make them fit.

The unfinished side edges of Angela’s mosaic look particularly neat because the sides of the ceramic tile is straight and not beveled like the sides of vitreous glass mosaic tile, which could still be used if you didn’t mind an edge that was a little rougher. Continue reading